The goal of this proposal is to utilize a targeted nanosystem to overcome and treat multi-drugresistant breast cancer. Breast cancer, like many cancers are highly prone to multi-drugresistance due to the overexpression of p-glycoprotein (p-gp). The main hypothesis is that paclitaxel containing lipid nanoparticles (NPs) targeted to the epidermal growth factor receptor (EGFR) using transforming growth factor-alpha (TGF-a)-coated nanoparticles may advantageously overcome resistance in human breast cancer cells over Taxol or untargeted NPs. Preliminaryin-vitro and in-vivo supports that these NPs may overcome resistance, and thus forms the basis of this proposal. The EGF-receptor is present in the majority of breast cancers and is present at very high levels as compared to normal cells. TGF-a has been shown to bind to a single class of high-affinity EGFR bindingsites with dissociation constant <5.3nM. The four year proposal has three Specific Aims, as follows: Specific Aim #1: Develop two improved pegylated (PEG) paclitaxel NP formulations;one being untargeted (PEG-NPs) and the other being targeted (TGF-a PEG-NPs) Specific Aim #2: Perform pharmacokinetic, biodistribution,and organ toxicity including hemocompatibility and histocompatibility studies in mice Specific Aim #3: Perform tumor efficacy studies with both untargeted PEG-NPs and targeted (TGF-a PEG-NPs) formulations versus Taxol in a nude mouse xenograft model bearing sensitive and resistant humanMDA-MB-231 breast cancer cells that overexpress the EGF-receptor (EGFR) A highly interdisciplinaryteam providing expertise in nanotechnology/drug delivery, clinicaloncology, and tumor biology has been assembled. Dr. Mumper's labs at the Universityof Kentucky will develop and characterize all NP formulations and perform in-vitro cytotoxicity, hemocapatibilitystudies, and in-vivo pharmacokinetic,biodistribution, and tumor efficacy studies. Dr. Adam's labs at the Universityof Kentucky will develop paclitaxel-resistant breast cancer cells, perform in-vitro and in-vivoangiogenesis studies, and assess EGFR expression both in-vitro and in-vivo. Dr. Tseng's labs at the University of Louisvillewill perform all structural analysis experiments relating to histocompatibility and the mechanisms of action of NPs in the breast cancer cells and endothelial cells. The innovation of this proposal relates to nanotemplate engineering of biocompatible nanoparticles, overcoming multi- drug resistance, and the use of nanotechnology to engineer a cell-targeted cancer therapy.